[00:00.70]Listen to part of a lecture in a biology class.
[00:05.30]Processor: Ok.[00:06.88] There are two major types of classifiers in the world, people we call lumpers and people we call splitters.[00:14.33] A lumper is someone who tries to put as many things as possible in one category.[00:19.70] Splitters like to work for the differences and put things in as many different categories as possible.
[00:25.70]Both lumpers and splitters work in the business of defining biological classifications. [00:31.31]The great philosopher Aristotle is generally considered the first person to systematically categorize things. [00:37.95]He divided all living things into two groups.[00:40.91] They were either animal or vegetable. [00:43.25]And these categories are what biologists came to call “kingdoms”.[00:47.33] So if it ran around, it was an animal, a member of the animal kingdom.[00:52.39] And if it stood still, and grew in the soil, it was a plant, a member of the plant kingdom.[00:58.66] This system, organizing all life into these two kingdoms, worked very well for quite a while, even into the age of the microscope.
[01:06.74]With the invention of the microscope, in the late 1500s, we discovered the first microorganisms.[01:13.70] We thought that some wiggled and moved around and others were green and just sat there.[01:19.46] So the ones that moved like animals were classified as animals, and the more plant-like ones as plants.[01:25.94] Oh, before I go on I must mention Carolus Linnaeus.[01:29.64] A hundred years or so after the invention of the microscope, Carolus Linnaeus devised a simple and practical system for classifying living things, according to the ranks of categorization still in use today——class, order, family and so on.
[01:44.66]And by further best aspect of the Linnaeus system, is the general use of binomial nomenclature, having just two names to describe any living organism.[01:54.50] This replaced the use of long descriptive names, as well as common names which vary from place to place and language to language.[02:02.09] Binomial nomenclature gives every species a unique and stable two-word name, agreed upon by biologists worldwide.
[02:11.44]But not everything about this system remained unchanged.[02:15.67] Take for example the mushroom, a fungus.[02:18.70] It grew up from the ground and looked like a plant.[02:22.20] So it was classified as a plant.[02:24.46] But using the microscope we discovered that a fungus contains these microscopic thread-like cells that run all over the place.[02:32.80] And so it’s actually not that plant-like.[02:35.74] So in this case, the splitters eventually won, and got a third kingdom just for the fungus.
[02:42.00]And as microscopes improved, we discovered some microorganisms that were incredibly small.[02:48.55] I’m talking about bacteria.[02:50.50] And we could see that they didn’t have what we call a nucleus.[02:54.05] So they got their own kingdom, a kingdom of very tiny things without nucleoli.[02:59.50] So then we had several kingdoms for plants and for animals, and the different kinds of fungus like mushrooms, and for these tiny bacteria.[03:07.90] But we also had some other microorganisms that didn’t fit anywhere.[03:12.41] So biologist gave them their own kingdom.[03:15.48] And this fifth kingdom was sort of anything that doesn’t fit in the first four kingdom, which upset some people.
[03:21.91]And then there was a question of viruses. [03:25.03]Viruses have some characteristics of life but don’t reproduce on their own or use energy.[03:31.27] So we still don’t know what to do with them.[03:34.20] The lumpers want to keep viruses in the current system.[03:37.37] Some of the splitters say to give them a separate kingdom.[03:40.54] And the extreme splitters say that viruses have nothing at all to do with living things and keep them out of my department.
[03:48.48]Recent research though has moved to see yet another direction.[03:52.63] Nowadays when we want to determine the characteristics of something, we look at its biochemistry and its genetic material.[4:00.22] And what we’ve discovered is that some bacteria are not like the others.[04:04.92] Many of these are called extremophiles. [04:07.77]They live in very strange places, in polar ice or in a boiling water of hot springs or in water so salty (that) other organisms couldn’t live there.[04:18.10] Extremophiles tend to have a different chemistry from other bacteria, a chemistry that in some case is actually more related to plants and animals than to previously known bacteria. [04:28.78]So what to do with this strange bacteria?
[04:33.19]Well, one thing we’ve done is creating a new set of categories, the domains, overarching the different kingdoms.[04:40.44] Biologists now recognize three domains.[04:43.66] But even as we talk about these new domains, well, come back in a few years and it might all be different.